Superficial angiomyxoma: clinicopathologic analysis of a series of distinctive but poorly recognized cutaneous tumors with tendency for recurrence.

Despite being first described in 1988, superficial angiomyxoma is still a poorly recognized cutaneous tumor. Although its histologic features are distinctive, its existence seems not to be widely accepted. We analyzed the clinicopathologic and immunohistochemical features in a series of 39 cases. Twenty-five patients were males; age range was birth to 82 years (median, 45.5 years). Most cases presented as cutaneous papules, nodules, or polypoid lesions. Seventeen tumors arose on the trunk, 14 on the head and neck, and seven on the lower limbs. All cases were treated by local excision, and eight recurred locally. In four of the latter cases, there were two recurrences. Histologically, the lesions were dermal with variable involvement of the subcutis. Tumors were poorly circumscribed, but a focal lobular outline was always identified. Distinctive histologic features included extensive myxoid stroma, numerous small blood vessels, varying cellularity, acellular mucin pools, stellate or bipolar fibroblastic cells, muciphages, a sparse, mixed inflammatory cell infiltrate with notable neutrophils, and occasional plumper cells with eosinophilic cytoplasm. Cytologic atypia was mild at most, and mitotic figures were rare. In approximately 20% of cases, the primary lesion or its recurrence contained epithelial structures, including epidermoid cysts, thin strands of squamous epithelium, and small buds of basaloid cells. Immunohistochemically, tumor cells were negative for S-100 protein, smooth muscle actin, and pan-keratin. We support the concept of superficial angiomyxoma as a distinctive clinicopathologic entity that should be included in the differential diagnosis of other myxoid cutaneous tumors, including dermal nerve sheath myxoma, trichodiscoma and trichofolliculoma, and low-grade myxofibrosarcoma.